1. Field of the Invention
The present invention relates to an intraocular optic, an intraocular lens, a corneal inlay, and a corneal onlay. More specifically, the present invention relates to an intraocular optic, an intraocular lens, a corneal inlay, and a corneal onlay having an apodization mask and/or a dynamic aperture for increasing depth of field. The mask and/or aperture may be in optical communication or integral with an ophthalmic lens that at least partially corrects a conventional error (lower order aberrations such as myopia, hyperopia, regular astigmatism, and presbyopia) and/or a non-conventional error (such as higher order aberrations) of a user's eye.
2. Description of the Related Art
There are two major conditions that affect an individual's ability to focus on near and intermediate distance objects: presbyopia and aphakia. Presbyopia is the loss of accommodation of the crystalline lens of the human eye that often accompanies aging. In a presbyopic individual, this loss of accommodation first results in an inability to focus on near distance objects and later results in an inability to focus on intermediate distance objects. It is estimated that there are approximately 90 million to 100 million presbyopes in the United States. Worldwide, it is estimated that there are approximately 1.6 billion presbyopes. Aphakia is the absence of the crystalline lens of the eye, usually due to surgical removal during cataract surgery. In an aphakic individual, the absence of the crystalline lens causes a complete loss of accommodation that results in an inability to focus on either near or intermediate distance objects. For all practical purposes, an individual will get cataracts if he or she lives long enough. Furthermore, most individuals with cataracts will have a cataract operation at some point in their lives. It is estimated that approximately 1.2 million cataract surgeries are performed annually in the United States.
The standard tools for correcting presbyopia are reading glasses, multifocal ophthalmic lenses, and monocular fit contact lenses. Reading glasses have a single optical power for correcting near distance focusing problems. A multifocal lens is a lens that has more than one focal length (i.e., optical power) for correcting focusing problems across a range of distances. Multifocal lenses are used in eyeglasses, contact lenses, corneal inlays, corneal onlays, and intraocular lenses (IOLs). Multifocal ophthalmic lenses work by means of a division of the lens's area into regions of different optical powers. Multifocal lenses may be comprised of continuous surfaces that create continuous optical power as in a Progressive Addition Lens (PAL). Alternatively, multifocal lenses may be comprised of discontinuous surfaces that create discontinuous optical power as in bifocals or trifocals. Monocular fit contact lenses are two contact lenses having different optical powers. One contact lens is for correcting mostly far distance focusing problems and the other contact lens is for correcting mostly near distance focusing problems.
The standard tool for correcting aphakia is an intraocular lens (IOL). A first type of IOL is a single vision or multifocal IOL that is non-accommodating and cannot change its optical power. A second type of IOL is an accommodating IOL that can alter its focusing power by way of example only, compression, translation, mechanical bending of a surface, or a combination of the above. Aphakia may also be corrected by using a single vision IOL in one eye and a multifocal or accommodating IOL in the other eye, or any combination thereof.
Alternate approaches are also being used to correct presbyopia. One approach is a corneal inlay that provides a small, fixed diameter aperture. By way of example only, the ACI 7000 corneal inlay made by AcuFocus is approximately 3.8 mm in diameter, 10 μm thick, and contains an opaque annulus with a 1.6 mm diameter transparent opening. This opening acts to reduce the aperture of the human eye to a smaller diameter than what is normally achievable by the natural constriction of the pupil.
As is well known in the art, limiting the diameter of the aperture of an optical system increases the system's depth of field. Depth of field is the distance in front of and behind the object plane that appears to be in focus on the image plane. Although an optical system can only provide for the precise focus of an object at the focal distance, in a system with increased depth of field, the decrease in sharpness on either side of the focal distance is gradual. Therefore, within the depth of field, the blurring produced on the image plane is imperceptible under normal viewing conditions. An aperture is used to increase depth of field by eliminating at least a portion of the light rays which make a large angle with the lens's optical axis (non-paraxial light rays). Non-paraxial light rays are only sharply focused when originating from objects located at the focal distance. For objects located at other distances, non-paraxial light rays have the highest deviation from the image plane. By eliminating non-paraxial light rays, the deviation from the image plane is minimized and objects located within a fixed distance of the focal distance (i.e., within the depth of field) appear in focus.
The small aperture counteracts some of the effects of presbyopia by creating a larger range of distances that appear in focus and allows presbyopes to conduct near vision tasks without the need for multifocal contact or spectacle lenses. The ACI 7000 is manufactured from bio-compatible materials whose optical properties are static, such as polyvinyldene fluoride or non-hydrogel microporous perflouroether, by way of example only. As such, once the inlay is placed within the cornea its refractive optical power is fixed.
The AcuFocus corneal inlay is designed to reduce the amount of light which reaches the retina. Additionally, the inlay is usually only be implanted in one eye as deleterious optical effects such as halos, doubling of vision, light scattering, glare, loss of contrast sensitivity, and/or reduction of light hitting the retina are too great and may be unacceptable when the inlay is implanted in both eyes. These deleterious effects are caused by the size of the inlay's aperture and occluded annulus in relation to the size of the pupil. These effects especially occur at night when the pupil dilates.
Another approach for correcting presbyopia is corneal refractive surgery in which one eye is corrected for far distance and the other eye is corrected for near distance. Another approach is a corneal inlay that provides a multifocal effect using diffractive optics, for example.
However, each of these approaches for correcting presbyopia and/or aphakia has drawbacks. Of course, some of these drawbacks are more severe than others. For example, while spectacle eyewear is capable of correcting one's vision for far, near and intermediate distances, this approach requires wearing a device that takes away from one's natural appearance. Also, in some cases, certain multifocallenses may cause the user to perceive distortion and experience vertigo.
Approaches for correcting presbyopia and/or aphakia that include the use of contact lenses can cause discomfort and can also result in one or more of: halos, doubling of vision, light scattering, glare, loss of contrast sensitivity, limited range of focus, and/or reduction of light hitting the retina. Approaches that include the use of IOLs can result in one or more of: light scattering, glare, halos, ghosting, loss of contrast sensitivity, limited range of focus, and/or reduction of light hitting the retina.
These drawbacks, or compromises to one's vision, can be very problematic especially, by way of example only, when driving at night, driving in the rain, or working on a computer. Therefore, there is a need for a superior mode of correction for presbyopia and/or aphakia.